Which factors are associated with bone marrow oedema suspicious of axial spondyloarthritis as detected by MRI in the sacroiliac joints and the spine in the general population?

Objective Identify factors associated with presence and extension of spinal and sacroiliac joints (SIJ)-MRI lesions suggestive of axial spondyloarthritis (axSpA) in a population-based cohort (Study of Health in Pomerania) aged <45 years. Methods Spinal (sagittal T1/T2) and SIJ (semicoronal STIR sequences) MRIs were evaluated by two trained blinded readers. The presence (yes/no) and extension (Berlin MRI Score) of bone marrow oedema (BME) were captured. Degenerative spinal lesions were excluded and discrepancies resolved by consensus. Cross-sectional associations between clinical factors and presence/ extension of BME were analysed by logistic/negative binomial regression. Record linkage of claims data was applied to identify participants with axSpA. Results MRIs of 793 volunteers were evaluated. The presence of SIJ-BME (odds ratio) was strongly associated delivery during the last year (4.47, 1.49-13.41). For SIJ-BME extension, associations (incidence rate ratios, 95% CI) were found for delivery ((during last year) 4.52, 1.48-13.84), human leucocyte antigen (HLA)-B27+ (2.32, 1.30-4.14), body mass index (25-30 vs <25 kg/ m(2); 1.86 (1.19-2.89)) and back pain ((last 3 months) 1.55, 1.04-2.31), while for spinal BME, associations were found for age per decade (1.46, 1.13-1.90) and physically demanding work (1.46, 1.06-2.00). Record linkage was available for 694 (87.5%) participants and 9/694 (1.3%) had a record of axSpA (ICD M45.09). Conclusion These population-based data support the hypothesis of mechanic strain contributing to BME in the general population aged <45 years and the role of HLA-B27+ as a severity rather than a susceptibility factor for SIJ-BME.

Automated summary

This population-based cohort study identified factors associated with MRI lesions suggestive of axial spondyloarthritis (axSpA) in individuals aged <45 years. The presence and extension of bone marrow edema (BME) in spinal and sacroiliac joints (SIJ) were strongly associated with factors such as delivery during the last year, HLA-B27 positivity, body mass index, and back pain. These findings support the hypothesis of mechanical strain contributing to BME in the general population aged <45 years and suggest that HLA-B27 positivity may play a role in severity rather than susceptibility to SIJ-BME.